What you don't know can hurt you -- especially if you have a case of disseminated Mycobacterium avium complex (MAC) infection. If so, you'll want to take heed of this overdue warning from the National Institutes of Allergy and Infectious Diseases (NIAID): "Treatment of [MAC] patients with clarithromycin [the antibiotic with the trade name Biaxin] should not exceed the approved dose of 500 mg twice daily."

The reason? The third clinical trial in a row found that a dose of 1,000 mg twice daily, also used by some community physicians, killed PWAs. The part of the NIAID trial comparing higher to lower doses of clarithromycin (in combination with ethambutol and either rifabutin or clofazimine) was stopped prematurely by the government's Data and Safety Monitoring Board after the high-dose arm experienced to 70 percent more deaths -- 17 compared to 10.

Although the board's action occurred February 6, NIAID waited until July 23 to issue a national clinical alert to physicians. The agency explained that "following last week's International AIDS Conference [in Vancouver], we became aware of renewed concern among HIV-infected persons" about the dosing danger.

That concern was forcefully expressed in a protest by several ACT UP chapters during a conference presentation by the trial's coordinator. John Riley of ACT UP/New York explains, "It was shameful that NIAID did a study which unnecessarily put PWAs at risk, did not provide informed consent, led to predictable 'excess deaths' -- and then was covered up until we blew the whistle. What quiet criticism from NIAID's community advisory group failed to do for five months, our action accomplished in 10 minutes."